Sauger
Sander canadensis are members of the Perciformes, the largest order of
vertebrates.Characteristics that
sauger share with most of the 9,200 other described species of fish in this
order include the presence of two dorsal fins with the first being spiny, no
adipose fin, thoracic pelvic fins, ctenoid scales, adaptation for life as a
predator, and small, free eggs and potentially widely dispersing larvae (Moyle
and Cech 2000).Sauger are part of
the family Percidae, which includes darters (Etheostoma, Percina, Ammocrypta),
perches (Perca), and pike-perches (Sander) (Moyle and Cech 2000).Sauger and walleye are the only extant contemporary North American
pike-perches (Billington et al. 1990).Sauger
can be differentiated from walleye by the presence of round dusky spots in
oblique rows between the rays of the spiny dorsal, the presence of scales on the
cheeks, and the absence of a pale lower caudal lobe (Brown 1971).

Distribution

Sauger
are one of the most widely distributed North American fishes with a historical
range extending across most of central and eastern North America from the St.
Lawrence-Champlain system south, west of the Appalachian Mountains, to the
Tennessee River in Alabama, and northwestward to central Montana and Alberta
(Scott and Crossman 1973).

In
Montana, historical distribution included the Missouri River and its major
tributaries downstream of Great Falls and the Yellowstone River and its major
tributaries downstream of the Clark Fork (McMahon and Gardner 2001).Current distribution in Montana has declined by 53% from historical
levels with the largest losses occurring in tributaries (McMahon and Gardner
2001).Current distribution in the
Missouri River drainage is confined to the mainstem Missouri and small parts of
the previously widely occupied Marias, Musselshell, and Milk rivers (McMahon and
Gardner 2001).Sauger are
considered rare or absent in other major tributaries such as the Teton, Judith,
and Poplar rivers (McMahon and Gardner 2001).In the mainstem Yellowstone River, distribution is now considered limited
to downstream of Rosebud Creek; sauger are considered rare or absent in major
tributaries such as the Big Horn and Tongue Rivers although a small, partially
isolated population may persist in the upper Powder River (McMahon and Gardner
2001; B. Stewart, Wyoming Department of Game and Fish, Sheridan, WY, personal
communication).

Life
history and ecology

Sauger
typically occur in large turbid rivers and shallow turbid lakes (Becker 1983).Turbidity is an important delineator of suitable habitat for
sauger.Physiological adaptations,
such as a highly advanced light-gathering retina, allow sauger to thrive in
low-light environments (Ali and Anctil 1977; Crance 1987).As cool water mesotherms, sauger have a fairly wide range of thermal
tolerance with occupied temperatures ranging from 1 to 30 C and a physiological
optimum of 18 to 24 C (Crance 1987; Carlander 1997).

Sauger
are heavily dependent throughout their life history on unimpeded access to the
wide diversity of physical habitats that are present in large river systems.They are considered to be the most migratory percid (Collette 1977).Their migratory behavior, which is primarily related to spawning, is well
documented throughout their range with annual movements of up to 600 km between
spawning and rearing habitats (Nelson 1968; Collette et al. 1977; Penkal 1992;
Pegg et al. 1997; M. E. Jaeger, Montana State University, unpublished data).Sauger are highly selective for spawning sites and commonly travel long
distances to aggregate in a relatively few discrete areas to spawn (Nelson 1968;
Nelson 1969; Gardner and Stewart 1987; Penkal 1992).Although mainstem spawning does occur, it has been suggested that sauger
populations are strongly reliant on access to large tributaries for spawning
(Nelson 1968; Gardner and Stewart 1987; Penkal 1992; Hesse 1994; McMahon 1999).Spawning locations are associated with unique geomorphic
features, such as bluff pools and bedrock reefs, and rocky substrates over which
sauger broadcast their eggs (Nelson 1968; Gardner and Stewart 1987; Hesse 1994).During a 10-12 day period following emergence, its thought that larval
sauger drift long distances downstream--up to 300 kilometers--prior to gaining
the ability to maneuver horizontally and begin feeding (Nelson 1968; Penkal
1992; McMahon 1999).Juveniles rear
in side channels, backwaters, oxbows, and other off-channel habitats during
spring and summer before shifting to main channel habitats in autumn (Gardner
and Berg 1980; Gardner and Stewart 1987; Hesse 1994).Adult sauger also use off-channel and channel-margin habitats during the
spring and early summer periods of high flow and turbidity, and then move to
deeper main channel habitats in late summer and autumn as decreasing flows and
turbidities cause suitable off-channel habitats to become unavailable (Hesse
1994; M. E. Jaeger, Montana State University, unpublished data).

Sauger
are piscivorous top predators for most of their lives (Collette 1977; Nelson and
Walburg 1977).During larval and
early juvenile stages, sauger feed on zooplankton and benthic invertebrates
before shifting to a diet of primarily fish by autumn of their first year
(Nelson 1968; Swenson and Smith 1977; Gardner and Stewart 1987).However, during times of low abundances of suitable prey fish, benthic
invertebrates make up part of the diet of juvenile and adult sauger (Preigel
1963; Swenson and Smith 1977).Sauger
are not highly selective piscivores and generally feed on a wide variety of
benthically oriented fish, including juvenile sauger, in proportion to their
relative abundance (Elser et al. 1977; Swenson 1977; Swenson and Smith 1977;
Preigel 1983).Much of their
feeding activity occurs crepuscularly (Carlander and Cleary 1949; Swenson 1977).

Sauger
mature sexually at 2 to 5 years of age (Carlander 1997).The maximum life span in Montana is about 8 years (Gardner and Stewart
1987; Penkal 1992; Carlander 1997).Sauger
year class strength is set by autumn of their first year and is thought to be
influenced most strongly by temperature and volume and fluctuation of streamflow
(Nelson 1968; Walburg 1972; Koonce et al. 1977; Carlander 1997; McMahon and
Gardner 2001).

Status

Sauger
have declined in abundance and distribution across their range (Rawson and
Scholl 1978; Hesse 1994; Pegg et al. 1997).They are globally currently ranked by NatureServe based on inventories
provided by state and provincial natural heritage programs as a �G5� species
of concern denoting that they are �demonstrably secure, though they may be
quite rare in parts of their range, especially at the periphery.�However, independent reports of sauger status throughout their range
suggest marked rangewide declines in distribution and abundance (Rawson and
Scholl 1978, Hesse 1994, Pegg et al. 1997, McMahon and Gardner 2001).Additionally, no information is currently available regarding sauger
status in many parts of their range. The contradictory or absent information
currently available lends a great deal of uncertainty to the true range-wide
status of sauger.

Sauger
are listed in Montana as a �S2� species of special concern by the Montana
Natural Heritage Program, Montana Department of Fish, Wildlife & Parks, and
the Montana Chapter of the American Fisheries Society (Carlson 2003).This designation indicates that sauger are �imperiled because of rarity
or because of other factors demonstrably making it very vulnerable to extinction
throughout its range� in Montana (Carlson 2003).The listing was prompted by statewide declines in distribution as well as
dramatic declines in abundances in all extant sauger populations in the late
1980s with only limited recovery observed subsequently (McMahon 1999; McMahon
and Gardner 2001).

Threats

Angler
harvest, channelization, water flow fluctuations, migration barriers, loss of
spawning and rearing habitat, and environmental degradation have resulted in
declines in distribution and abundance of sauger populations rangewide (Rawson
and Scholl 1978, Hesse 1994, Pegg et al. 1997).Similar factors have been implicated in the declines observed in Montana.Habitat loss and the presence of migratory barriers are the primary
causes of the reduced distribution of sauger in Montana (McMahon and Gardner
2001).Their highly migratory
nature, propensity to spawn in only a few areas, and reliance on a wide variety
of habitats throughout their life history combine to make sauger one of the most
sensitive percids to habitat alteration (Leach 1977; Hesse 1994; McMahon 1999).Impoundment of mainstem rivers and tributaries physically isolates sauger
from important spawning and rearing habitats as well as reduces turbidities and
alters the timing and magnitude of the hydrograph from the natural discharge
regime that sauger evolved in (Hesse 1994; McMahon 1999; McMahon and Gardner
2001).Mainstem and tributary
low-head irrigation diversion dams similarly fragment and degrade habitat and
cause additional mortality by entraining juvenile and adult sauger into
irrigation canals (Hiebert 2000; McMahon and Gardner 2001).Stream-bank stabilization and chronic or intermittent dewatering for
irrigation and power production have resulted in the loss of critical
off-channel habitats (Garner and Berg 1980; Hesse 1994).Loss of major spawning tributaries has also occurred as a result of
chronic dewatering for irrigation (McMahon and Gardner 2001).

Low
streamflow is believed to be the primary cause for the declines in sauger
abundances observed in the late 1980s throughout Montana (McMahon and Gardner
2001).Whether natural or anthropogenic in origin, low streamflow
can detrimentally affect sauger populations by stranding eggs (Nelson 1968),
limiting downstream transport of larval sauger (Nelson 1968; Gardner and Berg
1980; Penkal 1992), dewatering off-channel habitats (Gardner and Berg 1980;
Hesse 1994), and causing poor prey recruitment (Nelson and Walburg 1977).However, other factors such as overharvest, competition and hybridization
with walleye, and competition with other introduced piscivores have also been
suggested to explain the region-wide declines in sauger abundance and subsequent
poor recovery despite improved flows (McMahon and Gardner 2001).Of these non-flow related threats, expansion of and increased management
emphasis on walleye populations might be the most detrimental to sauger in the
long-term.Impoundment of mainstem
and tributary rivers create conditions more favorable to walleye populations
that, during times of low sauger abundance, can completely envelop sauger
populations into their gene pool (Rawson and Scholl 1978).Sauger are especially sensitive to these threats, and therefore
susceptible to resulting declines in abundances, because of the aforementioned
habitat loss, degradation, and fragmentation that has occurred in Montana.

Management
Opportunities

Mitigation
of habitat loss and fragmentation holds the most potential for recovery of this
species.Removal of mainstem and
tributary impoundments, which would restore natural flow and sediment regimes,
natural channel and habitat formation processes, and population and habitat
connectivity, would be the single most effective restorative action that could
be taken and holds far and away the greatest potential for recovery of sauger
and other imperiled large river fishes in Montana.Although such restorative measures are unlikely at this time,
other restoration potential does exist and is being pursued.Improved passage at several irrigation-related migratory barriers is
being planned and implemented.Similarly, fish screens and return structures have been
installed and more are planned to minimize entrainment of fish in irrigation
canals.Negotiations to restore
instream flows in some tributaries, especially during critical spring spawning
times, are ongoing.Flow releases
from mainstem dams can also be regulated throughout the year to maximize
spawning success and year-class strength of sauger (Nelson 1968; Walburg 1972).Angler harvest has been restricted to reduce fishing mortality in areas
where declines in sauger abundances are most marked.Supplementation of sauger populations by artificial propagation is being
attempted to bolster abundances and restore sauger to areas where they have beenextirpated.Levels of
introgression with walleye are being investigated to determine the threat to
sauger as walleye populations expand.Additionally, extant sauger populations are being closely
monitored and research is being conducted to fill information gaps to allow
managers to determine how and where restoration and conservation efforts can be
most effectively directed.

Conservation
of what habitat remains should also be recognized as essential to the recovery
and restoration of sauger in Montana.Montana
boasts some of the most pristine large-river habitat in the United States.Preservation of natural hydrographs, natural processes of channel
formation, and high degrees of connectivity where they currently exist should be
considered among the highest priorities for sauger conservation and recovery.Preservation of existing habitat can best occur by minimizing the
diversion of water from river channels and limiting processes such as
channelization and stream-bank armoring that result in loss of important
off-channel habitats.Additionally,
it is important that further disruptions to the connectivity of tributary and
mainstem habitats be prevented to avoid further declines in abundance and
distribution of sauger in Montana.

Information
Needs

Whereas
current research focusing on genetics, hybridization, interaction with walleye,
movement, exploitation, and habitat use of adult sauger will provide a wealth of
new information, several information gaps still limit the effectiveness of
sauger management in Montana.The
largest information gap that currently exists is related to early life history.Very little is currently known about which factors most strongly
influence spawning success, larval and juvenile survival, and, ultimately, year
class strength.Similarly there is
little knowledge of the specific habitat requirements and movements of juvenile
sauger.The effect of downstream
reservoirs and their water levels on sauger recruitment is also unknown.Whereas adult spawning locations, movements, and habitat use have been
determined for some Montana sauger populations, there is evidence that other
populations, specifically those using tributaries for spawning and rearing and
those residing in reservoirs, exhibit alternative life history patterns that
warrant further investigation.Addressing
these issues will provide managers with information necessary to more
effectively manage and enhance sauger populations.

Literature
Cited

Ali,
M. A., and M. Anctil.1977. Retinal
structure and function in the walleye (Stizostedion vitreum vitreum) and
sauger (S. canadense).Journal
of the Fisheries Research Board of Canada 34:1467-1474.

Gardner,
W. M., and R. K. Berg.1980. An
analysis of the instream flow requirements for selected fishes in the Wild and
Scenic portion of the Missouri River.Montana
Fish, Wildlife and Parks report, Great Falls, MT.

Nelson,
W. R.1968. Reproduction and early life history of sauger, Stizostedion
canadense, in Lewis and Clark Lake.Transactions
of the American Fisheries Society 97:159-166.

Nelson,
W. R.1969. Biological characteristics of the sauger population in
Lewis and Clark Lake.U. S.
Department of the Interior, Bureau of Sport Fisheries and Wildlife, Technical
Paper 21.

Nelson,
W. R., and C. H. Walburg.1977.
Population dynamics of yellow perch (Perca flavescens), sauger (Stizostedion
candense), and walleye (S. vitreum vitreum) in four mainstem Missouri
River reservoirs.Journal of the
Fisheries Research Board of Canada 34:1748-1763.

Pegg,
M. A., P. W. Bettoli, and J. B. Layzer.1997.Movement of saugers in the lower Tennessee River determined
by radio telemetry, and implications for management.North American Journal of Fisheries Management 17:763-768.

Penkal,
R. F.1992. Assessment and requirements of sauger and walleye
populations in the Lower Yellowstone River and its tributaries.Montana Department of Fish, Wildlife and Parks report, Helena, MT.

Priegel,
G. R.1963. Food of walleye and sauger in Lake Winnebago,
Wisconsin.Transactions of the
American Fisheries Society 92:312-313.